This invention relates to steerable catheters, for example, medical catheters used in angiography, endoscopy or angioplasty.
In general, the term catheter as used in this application includes a wide variety of devices for accessing a remote location, particularly medical devices for inspecting, assaying or operating on interior bodily tissue. For example, catheters may be used to sample tissue or fluid, or to administer drugs, radiation, heat, laser light, or an electric stimulus to a selected remote location. They may be used to inspect a remote location using fibre optics. Catheters also may be used for remote physiological measurements--e.g. heat, electrical impulses (EKG), pH, or chemical assays.
A wide variety of medical catheters are known; for example, catheters such as the cather disclosed in O'Leary U.S. Pat. No. 4,545,390 are used to dilate coronary arteries or to perform coronary angioplasty. Another common type of catheter is the endoscope.
Catheters also may be used industrially to access remote locations in equipment such as a heat exchanger having tortious tubing or spaces.
One serious difficulty with catheters is accessing the correct branch where a pathway (e.g. an artery) branches. For example, a catheter may be introduced into a coronary artery via another, more accessible artery, such as a femoral artery. The catheter must be advanced along the arterial system through numerous branches until it is properly located in a coronary artery. The physician inserting the catheter must advance it carefully, without damaging tissue, and without allowing it to venture into the wrong path. Access to the desired branches may require sharp bends first in one and then in another direction. It is highly desirable to be able to steer the catheter, yet the nature of the environment of use makes visualization and steering difficult.
Often guidewires may be used to advance the catheter, and catheters having steerable guidewires are known. For example, O'Leary U.S. Pat. No. 4,545,390 discloses a coronary dilatation catheter with a steerable guidewire. The guidewire has torsional rigidity to transmit a twist from the proximal end to the distal end. The distal end can be bent manually by the surgeon and will retain its bent configuration. The catheter is steered by rotation of the guidewire to direct the curved distal end selectively into the desired arterial branches.
Other steerable catheters are disclosed in Frisbie U.S. Pat. No. 4,619,263, Plerle U.S. Pat. No. 3,552,384 and Kaldenbach, European Heart Journal (1984) 5:1000-1009.
Takayama U.S. Pat. No. 4,503,842 discloses apparatus to control the deflection of the tip of an endoscope, by means of angulation wires secured to the distal end of the endoscope. The angulation wires are looped around wire drums which in turn are driven by motors. Other similar endoscope tip angulation control mechanisms are shown in Yamaka U.S. Pat. No. 4,483,326; Ouchi U.S. Pat. No. 4,461,282, Ogawa, U.S. Pat. No. 4,286,585 and Kruy U.S. Pat. No. 4,207,873.